1. Field of the Invention
The present invention relates to a method for regenerating multi-metallic platinum-containing hydrocarbon conversion catalysts. In a preferred embodiment, the present invention relates to a process for regenerating supported hydrocarbon conversion catalysts, containing both platinum and iridium which have been deactivated by the deposition of carbonaceous residues thereon during contact with a hydrocarbon feedstock at elevated temperatures.
2. Description of the Prior Art
The deactivation of noble metal-containing hydrocarbon conversion catalysts due to the deposition on the catalyst of carbonaceous residues is a well known phenomenon which has received much attention in the technical and patent literature. The problem with regard to catalyst deactivation is particularly acute with respect to supported noble metal-containing catalysts employed in the hydroforming of naphtha feedstocks.
Numerous methods have been suggested by prior workers for the regeneration of supported noble metal catalysts which have been deactivated by the deposition of carbonaceous residues. In U.S. Pat. Nos. 2,916,440; 3,243,384; 3,201,355; and 3,654,182 there are disclosed procedures utilizing gaseous mixtures containing oxygen and a halogen or halogen compound, particularly hydrogen chloride for combustion of a carbonaceous residue. Further in U.S. Pat. No. 3,378,419 there is disclosed the procedure for the regeneration of supported platinum catalysts involving (a) addition of halogen to the catalyst while in contact with the process feedstock; and (b) burning the coke deposits from the catalyst with an oxygen-containing halogen free regeneration gas. The prior art has also recognized that regeneration procedures previously practiced are not adequate for the regeneration of iridium-containing catalysts. Iridium-containing catalysts have been recognized as requiring special regeneration procedures in order to prevent the agglomeration of iridium and, in this connection, numerous patents have issued on various techniques for the regeneration of iridium-containing catalysts. Representative of such patents are U.S. Nos. 3,904,510; 3,937;660; 3,939,062; 3,941,682; 3,941,716; 3,943,052; 3,981,823; 3,998,755; 4,046,673; and 4,172,817.
Many of the prior art teachings with regard to the regeneration of multi-metallic platinum-containing catalysts and, in particular, platinum and iridium-containing catalysts were concerned with the prevention of or minimization of, the agglomeration of the non-platinum component during the coke burning step and all sorts of procedures were devised and disclosed in order to prevent said non-platinum component from agglomerating. Additionally, the prior art processes, in general, required very complex regeneration schemes which, in most cases, had to be repeated and did not lend themselves to ensuring an attractive regeneration process.